The strong and powerful 27-year-old Nigerian winger, previously with London Welsh and Richmond, played 25 games for Llandovery last season and scored 11 tries. He also broke into the Scarlets team with three appearances.
He said: "I'm really pleased to be signed up with the Scarlets now full-time and just look forward to the challenge ahead and working hard in pre-season to get myself in great shape. I know I need to work on the finer points of my game and I'm looking forward to being part of the Scarlets squad next season.
"Although I had some time with them last season, I'm new to the Scarlets mix and have plenty to learn from the guys around me - from simple things like the game language and team culture to the technical dynamics within the Scarlets environment. I'm really looking forward to be part of that next season and I'm eager to impress so will be doing all I can to learn quickly.
Head Coach Nigel Davies said: "Joe has speed and power and is a player with a lot to offer - he's one of those players with a certain X-factor and you need players like that in the mix in a team. He will benefit from being with us full-time and as part of his development contract will get mentoring not only from the coaches but also the senior players who will be helping him work on key areas of his game."
The Scarlets have also signed one-year full-time senior playing contracts with two promising young talents - flanker Aaron Shingler and hooker Emyr Phillips who were both on development contracts with the region last season.
Scarlets wing and Wales sevens player Darren Daniel, whose contract with the Scarlets came to an end this summer, will leave the region to join Carmarthen Quins next season. Daniel, who is from Burry Port has been with the Scarlets for five seasons, making 65 appearances and scoring 21 tries in total.